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I I I' I I I I I I II I I I I I I I I' I 2005 PAVEMENT MANAGEMENT PROGRAM D. PROPOSED DRAINAGElWATER QUALITY IMPROVEMENTS DRAINAGE OVERVIEW The majority of this business area drains overland or through an existing storm sewer system to the ditch along the TH 51 frontage road, Thc runoff continues to flow under TH 51 and into Lake Valentine via a meandering channel which runs through Bethel University. No storm sewer exists on Dunlap Street. Runoff from Dunlap Street and adjacent properties ends up ponding in ruts along Dunlap Street and ultimately flows south overland to Grey Fox Road. Dunlap Street runoff is therefore untreated when it enters the storm sewer. Other untreated runoff within this area includes runoff along Red Fox Road, Grey Fox Road and the TH 51 Frontage Road as well as runoff from the business parking lots adjacent to Dunlap Street. The remaining runoff within this project area is treated, generally in privately constructed ponds throughout the project area, prior to flowing into the storm sewer system, The proposed drainage improvements are illustrated in exhibits Al - A5 of the Appendix, Overall, the proposed improvements will not change existing drainage patterns with the exception of the areas that are untreated and within City ROW. The proposed water quality improvements include the following: The reconstruction of Dunlap Street includes the use of infiltration swales along the east and west boulevards to intercept runoff from adjacent parking lots thus reducing the load on the proposed storm sewer systcm and provide some level of treatment for area runoff. The infiltration swales will be constructed within the City ROW, will consist of mowable turf and will facilitate infiltration and sediment removal for small rainfall events, The sand subbase for the roadway (with draintile) will also be extended under the swale areas to promote maximum infiltration of runoff. During larger storm events, the infiltration swales will overflow into the street itself and be collected by catchbasins, which will route the runoff to an expanded ponding area along the northern edge of Grey Fox Road. The project includes reducing driveway widths wherever possible to help reduce runoff as well as improve traffic flow along the street. There are a number of driveways that are shared with multiple properties and are 40 to 70 feet wide. Specific driveways will be investigated and narrowed if appropriate &~ .~ II ,- - . . .._-.J.~_ ~ T~ . ...1fII '.:~:,"~ .: ,~_~..w'_~~~ _~~~~:. ..":;i': East side of Dunlap Street facing north - Potential infiltration swale location '" ,-' ~<- ~ ..,..,:.';..-....>..,...'..'.... ~,., :':.,,:_:.:.::----:7:;i..:;~~~, ~.". -"." ".". East side of Dunlap facing south - Potential infiltration swale location . ".~ URS 11